Indium sulfide thin films have been prepared by a novel modulated flux deposition procedure. Experimental parameters have been adjusted in order to obtain a high band gap and low absorption material at low deposition temperature, as required for photovoltaic applications. All samples showed tetragonal beta-In2S3 structure with random or preferential (103) plane orientation, depending mainly on the sulfur availability during the growth process. The sulfur availability has been optimized to achieve smooth surfaces and low scattering/absorption in the films. The average crystallite size decreased and the energy gap increased as the layer thickness decreased from 250 to 60 nm. Energy gap values as large as 3.02 eV have been obtained for the thinnest In2S3 films. (C) 2003 Elsevier B.V. All rights reserved.